2020年5月6日、5月9日，新疆地区南天山西段先后发生乌恰5.0级和柯坪5.2级地震，系统总结2次地震发生前出现的地震活动和地球物理观测异常，其中：①地震活动：震前存在调制地震集中、地震窗、5级以上地震成组等中短期异常；②地球物理观测：2次地震震中附近震前出现形变、电磁和流体观测异常，其中形变异常3项、电磁异常4项、流体异常1项，主要分布在柯坪5.2级地震震中附近。通过对2次地震序列进行跟踪，发现：乌恰5.0级地震余震较少，震后60天内共记录ML 3.0以上余震4次，最大震级为ML 4.5；柯坪5.2级地震后余震较丰富，震后60天内共记录ML 3.0以上余震10次，最大震级为ML 4.7，计算得到序列h值为1.6，b值为0.73。综合分析认为，2020年5月新疆地区2次5级以上地震前存在的地震活动异常较少，但区域地震活动水平较强，主要存在具有中短期指示意义的地球物理观测异常。
Two earthquakes with MS ≥ 5.0 occurred in the Tianshan seismic zone of the Xinjiang region on May 6 and May 9, 2020, respectively. This paper systematically summarized the observed seismicity and geophysical anomalies before the two MS ≥ 5.0 earthquakes. In terms of seismicity, there were medium-term and short-term anomalies such as modulated earthquakes concentration, seismic window, and the MS ≥ 5.0 earthquake group before earthquakes occurred. In terms of geophysical observations, including deformation, electromagnetism, and fluid anomalies near the epicenter of the two earthquakes, there were 4 electromagnetic anomalies, 3 deformation anomalies, and 1 fluid anomaly, which mainly distributed near the epicenter of the Keping MS 5.2 earthquake. According to the tracking process of the two earthquake sequences, the aftershocks of the Wuqia MS 5.0 earthquake are rare and there are only 4 aftershocks with ML ≥ 3.0 recorded within 60 days after the mainshock with the largest magnitude of ML 4.5. In contrast, there are abundant aftershocks of the Keping MS 5.2 earthquake, 10 aftershocks with ML ≥ 3.0 were recorded within 60 days after the mainshock, and the largest magnitude is ML 4.7. The h value of the Keping MS 5.2 earthquake sequence is 1.6, and the b value is 0.73. In summary, there were few anomalies of seismic activity before two MS ≥ 5.0 earthquakes, but the regional seismic activity level is strong. The geophysical observation anomalies were mainly medium-term and short-term.
2020,41(4): 179-192 收稿日期：2020-07-22
DOI：10.3969/j.issn.1003-3246.2020.04.023
基金项目：中国地震局震情跟踪定向工作任务（项目编号：2020010124，2020010122）
作者简介：马亚伟(1990-),男,主要从事地震活动性研究工作。E-mail:yawei_m@seis.ac.cn
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